Difference between revisions of "Dynamic memory allocation in C"
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3) '''Realloc''': | 3) '''Realloc''': | ||
Realloc is used when we have dynamically allocated memory and need to resize it. | Realloc is used when we have dynamically allocated memory and need to resize it. | ||
| − | Realloc can | + | Realloc can be used as a substitute to malloc or free. |
<syntaxhighlight lang="c"> | <syntaxhighlight lang="c"> | ||
int *ptr1 = (int *) realloc(ptr ,4*n*sizeof(int)); //dynamically allocated memory by malloc at pointer "ptr" will be increased 4 times in size. | int *ptr1 = (int *) realloc(ptr ,4*n*sizeof(int)); //dynamically allocated memory by malloc at pointer "ptr" will be increased 4 times in size. | ||
Latest revision as of 16:15, 27 April 2017
Malloc ,Callloc, Realloc, free:
1) Malloc: Malloc dynamically allocates requested memory and returns pointer to it.
/* We are allocating memory for "n" integers and returns integer pointer */
int *ptr = (int *) malloc(n * sizeof(int)); // We have type casted pointer to int2) Calloc: Calloc dynamically allocates requested memory and initializes it to zero. Calloc is compiler independent.
/* We are allocating memory for "n" integers and returns integer pointer */
int *ptr = (int *) calloc(n,sizeof(int)); // We have type casted pointer to int3) Realloc: Realloc is used when we have dynamically allocated memory and need to resize it. Realloc can be used as a substitute to malloc or free.
int *ptr1 = (int *) realloc(ptr ,4*n*sizeof(int)); //dynamically allocated memory by malloc at pointer "ptr" will be increased 4 times in size.
ptr1 = (int *)realloc(ptr1,0); //use realloc as free
int *ptr2 = (int *)realloc(NULL,n*sizeof(int)); //used as malloc
4) free:
After use of dynamically allocated memory, free the memory.
Consider below example:
free(ptr); // space pointed by pointer "ptr" is made available but the content in space is unchanged.
ptr = NULL;// NULL represents address 0 and it can not be dereferenced so ptr can not be dereferenced.
